Fungi are an increasingly important cause of death and morbidity in both immunocompetent and immunocompromised patients. Cryptococcal meningitis caused by Cryptococcus neoformans is the most common cause of fungal central nervous system infection in the world. One million cases of Cryptococcal infection occur globally, largely in the context of AIDS and constitute one-third of all AIDS-associated deaths. Despite these public health threats, effective treatments for cryptococcosis are inadequate. Recent reports indicate a high importance of genome plasticity in the pathogenicity of C. neoformans. For example, changes in chromosomal copy number are a major factor contributing to the resistance to the azole drug fluconazole in vitro and in vivo. The list of key resistance genes whose copy number increases in fluconazole-resistant C. neoformans isolates is well established. However, very little is known about the molecular mechanisms that govern changes in chromosomal copy number in this organism. The main objective of this proposal is to elucidate mechanisms responsible for generation of aneuploidy when C. neoformans is exposed to fluconazole. We will perform a detailed analysis of the effects of fluconazole on cell growth and nuclear division. In addition, we will elucidate basic architecture of the spindle assembly checkpoint (SAC) pathway in C. neoformans, and explore the possibility that the inhibition of this pathway is one of the causes of fluconazole-triggered aneuploidy leading to drug resistance. This work will contribute to our understanding of the mechanisms that are involved in chromosomal changes of a fungal pathogen during infection. This project will engage graduate and undergraduate students and allow for hands-on research experience. Students will be exposed to various laboratory techniques and will learn formulating and testing research hypotheses.